While this is true, you actually do have to be able to sustain a certain amount of healing during rampages. Which means it does depend on your healers if you can 2heal or 3heal. But so many other classes that aren't healers have a lot of CDs they bring to the table that you can use in order to survive.
We make use of everything we can (probably more than is needed to be honest.. but if you got it, use it). HTT or AG, and VE. Even the DK tries with putting up AMZ though it only lasts for a split second... I think he felt left out. :P
On topic, our team is having no problems with rampages but things seem to fall apart between the rampages later on. Which kill order do people think is best (we're trying grgrbrg)...
When we were 3 healing we did the order you are doing now. Blue annoys me because it kept focusing me over and over and over. It was, for us, necessary though because stacks were getting too high on our monk tank and he was splatting.
Honestly though, I would consider dropping to 2 healers and just doing G/R. IMHO, the last 2 weeks we have 2 healed it's been much easier than it was to 3 heal.
edit: If you are already two healing, I would take blue out of the mix, it's a completely unnecessary annoyance.
edit: To clarify the "easier" bit. Rampages were never the issue (as they don't seem to be the issue for you either) they were always incredibly easy to heal through. We ran into problems with acid rain/cinders in between rampages. Dropping a healer made for significantly less poop to kill us.